Add initial project structure and documentation

- Created architecture documentation outlining high-level design, module organization, data flow, security model, performance considerations, testing strategy, and deployment architecture.
- Added pyproject.toml for project metadata and dependencies management.
- Introduced requirements files for development and production dependencies.
- Set up testing configuration with pytest and tox.
- Established basic directory structure for source code and tests, including __init__.py files.
- Implemented a sample web application (index.html) for drag-and-drop functionality.
- Configured VS Code workspace settings for Python development.

tests/conftest.py

@@ -0,0 +1,21 @@
+"""Test fixtures and utilities."""
+
+from pathlib import Path
+from tempfile import TemporaryDirectory
+
+import pytest
+
+
+@pytest.fixture
+def temp_test_dir():
+    """Provide a temporary directory for tests."""
+    with TemporaryDirectory() as tmpdir:
+        yield Path(tmpdir)
+
+
+@pytest.fixture
+def sample_test_file(temp_test_dir):
+    """Provide a sample test file."""
+    test_file = temp_test_dir / "test_file.txt"
+    test_file.write_text("Test content")
+    yield test_file